This is nothing to get excited about. Pretty much anyone with a web page can be an Amazon or B and N affiliate. They check the site for obvious problems, (hate speech, racist speech, offensive images, porn) but it's not a big deal.

The Amazon Advantage program is not difficult to "join" either, though it's not cost effective. I've joined in the past (well, filled out the forms etc.) for an undergraduate literary journal, simply because Amazon's terms were still better for the undergraduates than the distributor they had been using. Using Amazon was a simpler way to distribute extra copies to the few libraries and parents who wanted to buy them.

In other words, participation in these programs is not a seal of approval.